Somerset 149 for 2 (Kieswetter 103) beat Durham 147 (Trego 3-26) by eight wickets
Craig Kieswetter continued his superb form with a hard-hitting 103 as Somerset moved off the bottom of Clydesdale Bank 40 Group B with an eight-wicket victory over Durham at Taunton.
Fresh from his match-winning 152 in the LV= County Championship success over Warwickshire on Saturday, Kieswetter plundered nine fours and six sixes in his 61-ball innings as Somerset overcame Durham's 147 with almost half their 40 overs to spare.
Gareth Breese top-scored for Durham with 31 not out, while Peter Trego removed three of the top four to finish as Somerset's most successful bowler with 3 for 26 in six overs.
More good news for Somerset was the return to action of former England batsman Marcus Trescothick, three months after he ruptured ankle ligaments while fielding against Nottinghamshire at Trent Bridge.
Trescothick made 15 from 17 deliveries before being bowled by Chris Rushworth and, having proved his fitness, now looks set to lead Somerset in Tuesday's Friends Life t20 quarter-final against Essex at Taunton.
Durham, with three wins from their previous six CB40 games, were always struggling once Trego had ripped through the top order. He had Phil Mustard caught behind off the last ball of the first over and Johann Myburgh taken at cover by Jos Buttler in his next.
Then, after Craig Meschede had Paul Collingwood caught at cover by Max Waller, Trego struck again when he held a return catch to dismiss Mark Stoneman, which made it 34 for 4. A fifth-wicket partnership of 33 between Ben Stokes and Gordon Muchall transpired to be Durham's best of the innings, but it came to an end when Stokes was caught on the mid-wicket boundary by James Hildreth off leg-spinner Waller.
Waller claimed his second wicket, when Muchall chipped to Trescothick at short mid-wicket, and then provided the direct hit which ran out Dale Benkenstein to make it 96 for seven. Alfonso Thomas had Scott Borthwick lbw for a duck and the veteran seamer went on to finish with a very economical return of 1 for 12 in seven overs.
Mitchell Claydon made an aggressive 18 before being caught behind down the leg-side off Lewis Gregory. Breese played well for his unbeaten 31, but Durham's innings ended when Rushworth was bowled by Gregory and a total of 147 never looked likely to trouble Somerset's formidable batting line-up.
Trescothick hit a couple of boundaries - a late cut off Myburgh and a back-foot force off Rushworth - before he was bowled by a slower delivery from the latter. It turned into the Kieswetter show after that as the England one-day international wicketkeeper peppered the boundary boards.
Kieswetter hit two sixes off Claydon in the seventh over, the first deposited over extra cover and the second over mid-wicket. He brought up his half-century from 38 balls and required only 20 more to register his hundred.
His four remaining sixes were all struck down the ground. The first came off Borthwick's leg-spin, the next off Collingwood and then the last two were taken from successive Claydon deliveries.
Kieswetter's remarkable innings ended in the 18th over when he holed out to Borthwick on the long-on boundary off Rushworth, which left Nick Compton and Hildreth to complete a comfortable victory.